It runs on a toothed white nylon "belt"; exactly like the antenna mast does.

May even be the same size as the antennae mast drive (can't remember size).

Your motor and switch are working, since you can hear the motor run, so a broken "belt", cord, whatever you want to call it, is the most likely culprit. Could be the gear assy. that drives the cord, but cord itself is more often the fault. FWIW. Was on mine.

Dealer part, not too expensive; but the antenna cord may work.

__________________
The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)